The subject of this invention is a transfer suction roll for transferring a material web from one machine section to a subsequent machine section. The transfer suction roll consists of a perforated suction roll shell that is pivot-mounted in roller bearings and a suction box mounted inside the transfer suction roll. The suction box is open along one longitudinal side facing the suction roll shell and defines a suction zone on the perforated suction roll shell by means of seals.
Transfer suction rolls are used to transfer a material web from one machine section to the next. In paper and board machines, transfer suction rolls are used, for example, to transfer the web from the wire section to the press section and from the press section to the dryer section. If there are several presses, transfer suction rolls are also used inside the press section.
In order to be transferred, the material web is taken from one machine section via a perforated roll shell by means of negative pressure in the transfer suction roll, held on the roll shell, and transferred to the next machine section at the end of the negative pressure zone. The zones to which suction is applied with negative pressure are the so-called suction zones. There are transfer suction rolls with one or several suction zones.
FIGS. 1 to 3 show a conventional transfer suction roll 1. FIG. 1 contains a longitudinal section and FIG. 2 a cross-section through a conventional transfer suction roll 1. It generally consists of a rotating, perforated roll shell 2 with hollow journals screwed to either side. The roller bearing assemblies 5 with the bearing housings 8 are provided on either side of the transfer suction roll 1. The fixed bearing housings 8 are bolted to the machine frame. There is a stationary suction box 4 inside the transfer suction roll 1. The suction box 4 has at least one vacuum connection 6 for the required negative pressure and holds the seals 13 in the suction zone 12 towards the zone without suction on the roll circumference. During operation, the material web 17 is wrapped round the suction roll shell 2 in the area of the suction zone 12.
The suction box 4 is swivel-mounted on both sides in the outer bearing covers 7. With a slewing gear comprising a worm gear 9 and a worm wheel 10, the entire suction box 4 can be rotated round its own axis. In this way, the position of the suction zone 12 can be adapted to the operating conditions.
The embodiment with vacuum-assisted suction box 4 has large cross-sections because of the air volumes to be discharged and thus correspondingly large and expensive (mainly forged) hollow journals 3. The roller bearings 5 of conventional transfer suction rolls 1 therefore have a correspondingly large diameter and are expensive as a result. In addition to the drilled suction roll shell 2, the hollow journals 3 and roller bearings 5 are the most time-critical components (long procurement times).
The sealing arrangement 13 in conventional suction zones 12 usually contains sealing strips 14 made of plastic (FIG. 3). The sealing strips 14 are supported movably in guide strips 15 and are pressed against the inner wall of the perforated roll shell 2 by means of inflatable compressed air hoses 16 made of elastomer material in order to guarantee the sealing effect. The hoses 16 must be supplied with compressed air from the outside.
In order to reduce wear, the sealing strips 14 are lubricated by water showers 11 (FIG. 2). The water showers 11 are secured to the suction box 4 and must be supplied with water from the outside. After some time, the sealing strips 14 are worn and must be replaced.
The adjusting device for the suction zone 12 with a worm gear 9, 10 is a complicated design and thus involves corresponding costs (worm gear 9, 10 worm gear wheel 10, bearings, . . . ).